Doses and bunch by bunch fluctuations in Beam
Doses and bunch by bunch fluctuations in Beam. Cal at the ILC Eliza Teodorescu FCAL Collaboration Meeting June 29 -30, 2009, DESY-Zeuthen, Germany
Beam. Cal Suport tube (Iron) Absorber (W) Electronics Sensor Dead Area sandwich em. calorimeter: 30 layers of 1 X 0 30 X 0 Ri = 20 mm R 0 = 150 mm Re = 50 mm RTi = 200 mm RTo = 250 mm 3. 5 mm W + 0. 3 mm sensor Ri ~ 104 - 105 channels of ~0. 8 RM Ro RTi Re RTo ~ 20 mm < R < 150 mm (200 electronics 250 suport tube) each sensor layer divided into 8 sectors
The simulation chain Simulate Collision: Guineapig OUTPUT (nominal parameter set) e+e- pairs ASCII File INPUT Simulate detector: Be. Ca. S 1. 2 OUTPUT full GEANT 4 simulation => energy, particle distributions … ROOT file Be. Ca. S A Geant 4 Beam. Cal simulation (A. Sapronov) Can be configured to run with: • different crossing angles (corresponding geometry is chosen): here: 14 mrad • magnetic field (solenoid, (Anti) DID, use field map): here: Anti DID
Electron-positron background energy deposition vs. calorimeter depth: - the maximum of the shower in the 5 th and 6 th layers, ~30 Ge. V/bx - Edep < 5 Ge. V/bx in the first sensor layer and in the second half of Beam. Cal 5 BX 1 BX
Electron-positron background Energy depositions along the sensor’s radius (layer 6) -statistics of 5 bunch-crossings -most of the energy is deposited in the innermost region of the sensor , then gradually decreases toward the outer radii - energy deposition decreases to less than 1% at a radius of about 80 mm - less than 0. 1% at 100 mm 5 BX
e+e- DOSE 3 x 10^11 BX/year the absorbed dose in the sensor layers 5 BX
e+e- DOSE The dose at different distances from the beampipe Closest to the beampipe: dose vs. layer number distribution : - the dose rises from 4 x 10^5 Gy/year (first layer) to 6 x 10^6 Gy/year (maximum), then slowly decreases to less than 2 x 10^4 Gy/year in the last layers of Beam. Cal. 5 BX 6 x 106 Gy/year (max) 4 x 105 Gy/year (front) 2 x 104 Gy/year (back) R = 20 mm-28 mm
The dose at different distances from the beampipe 5 BX e+e- DOSE 5 BX R = 150 mm-158 mm R = 100 mm-108 mm The innermost rings of the sensors are most affected Increase in the dose toward the final layers of Beam. Cal 2 causes: - natural developement of the shower - backscattered particles (from QD 0)
e+e- DOSE - remove QD 0 from simulation: dose slowly decreases 5 BX R = 100 mm 5 BX R = 150 mm
Bunch by bunch fluctuations Energy deposition and standard deviation for the whole calorimeter - one BX • each pad – independently read -> interesting to see how energy deposition fluctuates from bunch to bunch, in each pad • For this: (r, j) energy distributions • First: one BX (comparison with older results provided by Ch. Grah) 1 BX Christian Grah -closest to the beampipe – highest energy deposition ( ~10 Me. V/pad) - for the outer pads ~ke. V - there are pads with no energy deposition
What happens for more bunches? Bunch by bunch fluctuations - Simulate more bunch crossings and find the medium energy deposition - In this case: N=40 BX - Calculate the standard deviation: 40 BX Ø Energy deposition: • tens of Me. V – innermost pads • ke. V – rest of the pads Øs • 0. 1 Me. V – innermost pads • Ke. V – rest of the pads Mean Edep s
Bunch by bunch fluctuations Energy deposition for a single high energetic electron - 250 Ge. V initial energy - hits the first layer of Beam. Cal
Bunch by bunch fluctuations Shower development throughout the calorimeter – 250 Ge. V electron Layer 6 Etot = 0. 000132 Ge. V Layer 12 Etot = 0. 000398 Ge. V Layer 25 Etot = 2. 9 x 10 -5 Ge. V
Bunch by bunch fluctuations Superimpose the high energetic electron over the backgroud
Bunch by bunch fluctuations Ø Typical layer of average background with high energetic electron Ø Typical layer of background standard deviation with high energetic electron All BX Layer 6 Layer 12
The distribution of the average deposited energy and standard deviation in a pad (layer 12)
Thank you!
- Slides: 17